Tractor steering control



Patented Apr. 20, 1948 TRACTOR STEERING CONTROL I Arthur N. Milster, Ferguson. Mo., assignor to Wagner Electric Corporation, St. Louis, Mo., a

corporation of Delaware Application January 23, 1946, Serial No. 642,837

1 9 Claims.

This invention is related to tractor steering controls and in its more specific aspects discloses a mechanism employing two manually-operated pressure producing devices with means to selectively actuate one or both of two brake mechanisms associated with the drive wheels of the tractor to assist in the steering thereof.

Another object of the invention is to provide a tractor steering control employing individually manually-operated pressure producers, one for each of two brake mechanisms, and a device connected between the pressure producers and the brake mechanisms whereby under one operative condition of said device both brakes may be equally energized to brake the tractor from either one of said pressure producers, and in which under another operative condition of said device said pressure producers may selectively actuate the two brake mechanisms to assist in the steering of the tractor whenever a manually-operable tractor control is adjusted to certain predetermined positions.

Various devices have been developed in the art for employment in connection with tractors of both dirigible wheel and tractor wheel or tracklaying types of traction elements, in which one of the wheels or treads is left free to rotate while the other is braked in order to assist in the steering 01' such devices under certain operating conditions. The fluid pressure producers, commercially known as master cylinder, have been proposed to actuate the brakes for both steering assistance and stopping but in any such system embodying more than one standard compensating type of pressure producer, means must be provided to block the compensating portholes of the first pressure producer when the second is in use and vice versa. If this is not done, pressure fluid displaced from either cylinder will escape through the compensating port of the other and no pressure can be built up. This invention discloses means to prevent transfer of fluid from one pressure producer to the other and thereby enables all pressure produced by either pressure producer to be expended on the braking mechanism during operation.

In the drawings Figure 1 is a schematic view, partly of a tractor steering control;

Figure 2 is a sectional view taken along the line 2-2 of Figure 1;

Figure 3 shows left end parts in Figure 1 in adjusted position; and

Figure 4 shows an exploded view of a portion of the device of Figure 1.

in section,

2 The objects and advantages set forth above are achieved in the structure disclosed in the drawings in which numeral I is a manuallyoperated pressur roducer mounted on the vehicle frame and known as a master cylinder,

whose detailed construction is set forth in United States Patent No. 1,758,671, issued May 13, 1930, and is operated by a suitably mounted vehicle supported pedal 2. A second pressure producer 3, suitably supported on the tractor frame and similar in construction to pressure producer I,

is likewise actuated by a vehicle supported pedal 4. Piston rods 5 and 6 operatively connect brake pedals 2 and 4 with the pistons in the pressure producers l and 3. Each pressure producer is provided with a'compensating port la whose function is well known in the art.

. A control valve I is interposed in the connection between the pressure producers l and 3 and brake mechanism 8 for the right-hand drive wheel and brake mechanism 9 f)! the left-hand drive wheel. Each brake mechanism has shoes I0, l0 and H, II pivotally secured to backing plates l2 and I3. Suitable pressure fluid brake operating motors l4 and [5 are associated with back-- ing plates I 2 and I3, respectively, to expand brake shoes l0, l0 and H, II into engagement with the brake drum (not shown) customarily associated with the brake assembly.

Valve 1 comprises a suitably shaped housing l6 which has a projection or boss l associated therewith in which a suitable conduit I8 is threaded to connect the outlet side of pressure producer I with valve 1. The right-hand end of housing Hi has a fitting l9 threaded therein which receives a conduit 20 likewise threaded therein which is connected tothe outlet side of pressure producer 3.

Housing I6 is suitably bored to receive sleeves 2| and 2 I a which are securely brazed therein with gaps 54, 55 between them, these gaps or passageways being comparatively narrow whose length is determined by the length of projection 21b and He on sleeves 2| and 2| a, respectively, in Figure with spring 28 acting against a spring tension 3 adjusting screw 39 threaded into the bore of fltting l9. Spring 29 abuts against the wall portion in which the reduced diameter bore 25 is formed and under normal conditions of operation springs 29 and 29 keep the piston centrally disposed with respect to the bore in which said piston 22 slides.

Means have been provided to prevent the movement of piston 22 in its bore under certain conditions of operation of the tractor, it being desired under such conditions that either one of the brake mechanisms 8 and 9 may be operated selectively, thereby assisting in. the steering of the tractor and that under all other conditions of operation both brake mechanisms are to be operated by either pressure fluid producer to arrest motion of the tractor.

The foregoing result may be obtained by a mechanism associated with any low speed operation of the tractor or a device driven during slow speed movement thereof but is preferably controlled by a gear shift lever 3| ordinarily associated with the tractor transmission which has a, suitable lever 32 operatively associated therewith that is received in slot 33 of a lever 34. This lever is rigidly secured to a shaft 35, associated with valve 1, in order to rotate said shaft in a bushing 36 threaded into a fixture 31 which is threaded or otherwise secured in the left-hand end of housing l5. Lever 34 is appropriately secured to shaft 35 by bending and passing it through suitable apertures formed therein. Shaft 35 has a cam 39 secured thereto which is preferably of the multiple lobe variety and is engageable with a pair of levers 39 and 49 received in a bore formed in housing l6. An ex pansion spring 4| 'operatively engages levers 39 and 49 to urge them to the position illustrated in Figure 1. Rotation of cam 33 will cause the levers to pivot about fulcrums 42 and 43, thereby bringing the hooked ends 45 into groove 26 formed in piston rod 24 and the opposite ends of the levers 39 and 49 will assume the positions shown in Figure 3 wherein the cam operated ends of the levers move into the space 44. The condition necessary to bring the hooked ends 45 of levers 39 and 49 into groove 25 is during the low lock piston 22 in the position indicated by'bringspeed adjustment of shift lever 3| or when the y tractor is connected to any device operable at or responsive to low tractor speeds, and when shift lever 3| is set to high or any intermediate. speed spring 4'| will maintain levers 39 and 49 in the positions illustrated in Figure 1.

Conduit 46, which is threaded into housing I5, connects the brake motor l4 therewith, and conduit 41 in like manner connects brake motor I5 with housing l5. A passageway or duct 49 formed in housing l5 permits the transmission of pressure fluid originating in producer, I to be admitted into space 49 to the left of piston 22 and by means of passageway 54 and duct 59 formed .in housing Hi the pressure fluid is conducted from space 49 into conduit 95 to brake'motor l4. Pressure fluid developed by pressure producer 3 is transmitted through conduit 29 and is then conducted through bore 5| formed in adjusting screw 39 to a space 52 to the right of piston 22 and thence is conducted through duct or passageway 55 and duct 53 formed in the wall of housing IE to conduit 41 and then to brake motor l5.

The operation of this device, when used to assist in steering under load and in low speed operation, requires the operator to place the gear shift lever 3| in low gear position. Lever 32, which associates gear shift lever 3| with lever ing hooks 45 on levers 39 and 49 into groove 23 in piston rod 24, as illustrated in Figure 3. Piston 22 will remain in locked position as long as gear shift lever 3| is in low gear position. Under this condition the pressure fluid produced by pressure producer will be transmitted through conduit l9, through duct 48 into space 49, thence through passageway 54 into duct 59 and conduit, 45, and to brake motor H of brake 9 to brake the righthand wheel and permit the left-hand drive wheel to continue rotation about the right-hand wheel as a pivot to thereby assist in the steering of the tractor to the right. When it is desired to steer in the opposite direction, pressure producer 3 is actuated whereupon pressure fluid will flow through conduit 29 into space 52, through passage 5l, thence through passageway 55 into duct 53. conduit 41, and into brake motor l5, thereby causing the left-hand wheel to be held at rest or have its motion retarded, causing the righthand wheel to pivot about the left-hand wheel and thereby assist in the steering of the device to the left. When gear shift leverv 3| is placed in position for high speed travel or any intermediate speed, cam 39 will not actuate levers 39 and 49, thereby permitting piston 22 to move in its bore into space 49 or 52.

When it is desired to brake both wheels of the tractor, it can be done by actuating either of the pressure producers or 3 whereupon, assuming that pressure producer is actuated, fluid pressure produced thereby will flow through conduit l8, thence through duct 49 into space 49 and will then force the piston to the right until it abuts against the end of fitting l9, thereby placing the pressure fluid produced by'producer I in communication not only with duct 59 but also with duct 53 and thus transmitting pressure fluid through passageways 54, 55 and conduits 49, 41 to brake motors l4 and IS. The forcing of piston 22 and its packing 23 to the extreme right position prevents the passage of pressure fluid to conduit 29 and out through compensating port la into thefluid reservoir associated with pressure producer 3 and causing the entire output of pressure producer I to be directed to brake cylinders l4 and i5.

Assuming that pressure producer 3 has been actuated during the high speed condition of the vehicle, the fluid pressure produced thereby will travel through conduit 29, thence through passage 5| into space 52 forcing piston 22 to the left to place passageways 54 and 55 in communication therewith and then through passageway 53 into conduit 41 and also transmitting the pressure fluid produced by producer 3 through duct 59 into conduit 46 to brake motors I5 and I4, respectively, thereby actuating both brakes to stop the vehicle. This movement of piston 22 and packing23 to the extreme left will prevent fluid displaced by pressure producer 3 passing to pressure producer I and thence through compensating port la to the fluid reservoir associated with the pressure producers. It will thus be observed that fluid pressure developed in either pressure producer cannot be dissipated through the compensating port Ia of the other pressure producer, as would be the case if conduits l8 and 29 were not sealed from each other by piston 22 and its 1. A tractor steering control comprising a valve ;having a movable piston therein: two manually-operated pressure fluid producer's; brake mechanisms for the right and left-hand drive wheels of a tractor; a manually-operated 5 speed controlling device; and means controlled by said manually-operated device when in certain positions of adjustment to lock said piston in position in said valve to enable saldfbrake mechanisms when selectively actuated to assist in in steering the tractor and said manually-operated speed control when in other positions of adjustment enabling either one of said pressure producers to actuate both of said brake mechanisms, said piston preventing transfer of pressure fluid from one pressure producer to the other when either one operates both brake mechanisms.-

2. A. tractor steeringncontrol comprising two manually-operated pressure fluid producing devices; a valve mechanism having a movable piston therein; two brake mechanisms, means to connect said devices to said valve mechanism, each device connected to opposite ends of said valve mechanism and acting on opposite sides of said piston, means to connect each brake mechanism with opposite ends of said valve mechanism; a speed control; means associated with said speed control and engageable'with said piston to lock piston preventing transmission of pressure fluid from the actuated pressure fluid producing device to the idle pressure fluid producer.

3. A tractor steering control comprising a pair of independently operated brakes each of which is associated with one of the driving wheels of a 40 tractor; a pair of manually-operated pressure fluid producers; a valve; conduit means connected to said valve and to each of said producers and said brake mechanisms; a movable element in said valve so associated with said conduit connections that each of said pressure producers operates one of said brake mechanisms; a speed varying means; and means associated with said valve and connected to said speed varying means to lock said movable element in position under a predetermined adjustment of said speed varying means to enable said manually-operated pressure producers to selectively operate said brake mechanisms, said speed varying means when in other positions of adjustment releasing said movable element, and when either one of said manually-operated pressure fluid producers is operated it moves said movable element in said valve to allow said operated manually-operated producer to actuate both of said brakes, said movo able element when moved in said valve segregatsaid tractor to lock" said piston tor-selective operation oi said motors and their associated brake mechanisms, said piston being freely movable in said valve during-,all other tractor speeds and movable to one oi two'extreme positions in said valve by a selected pressure producer to enable same to actuate both mechanisms, said piston thus preventing transmission of pressure fluid to 'the idle pressure producer.

5. A ti'actor steering control comprisinga brake mgqhanism for each or the two traction wheels of a tractor; a first pressure fluid producer, a-

said valve to enable said brake mechanisms to be.

selectively operated, said third means when in another position of adjustment-releasing said movable member and enabling it to be moved by pressure fluid from one of said pressure fluid producers vto enable the last mentioned pressure fluid producer to operate both brake mechanisms.

6. A tractor steering control comprising a pair of brake mechanisms; a first pressure fluid producer to operate one of said brake mechanisms;

a second pressure fluid producer to operate the other of said brake mechanisms; a valve interposed between said brake mechanisms and said pressure fluid producers; a movable member in said valve to prevent the establishment of communication between said pressure fluid producers; and means to position said member in said valve so that said pressure fluid producers may selectively operate said brake mechanisms, said member movable in said valve by either of said pressure fluid producers and when said means is dissociated from said member the pressure fluid producer operated positions said member so that both of said brake mechanisms may be operated by said last mentioned pressure fluid producer.

7. A tractor steering control comprising a brake operating motor for each ofthe two traction wheels of a tractor; a .flrst pressure fluid producer to operate one of said motors; a second pressure fluid producer to operate the other of said motors; a control valve interposed between said motors and said pressure fluid producers; a movablemember in said valve to prevent the establishment oi. communication between said pressure fluid producers; a gear shift lever adjust'able to a plurality of positions; and means to connect said lever to said movable member when said lever is in one position of adjustment so that said motors may be individually operated, said member being disconnected from said lever when it is in other positions of adjustment so that said member is movable by pressure fluid derived from either of said pressure fluid producers to enable both motors to be operated by one of said pressure fluid producers.

8. A tractor steering control comprising a motor for the brake mechanisms associated with each of the two drive wheels of a tractor; apressure fluid producer to operate one of said brake motors; a pressure fluid producer to operate the other of said brake motors; valve means interposed between said pressure fluid producers and said motors; a movable member in said valve to prevent the establishment of communication between said pressurev fluid producers; a gear shift lever adjustable to a plurality of positions; and means to connect said lever to said member when the lever is in one position of adjustment to prevent movement of the movable member so that said motors may be individually operated, and when said lever is in other positions of adjustment said movable member is disconnected from said lever so that when one of said pressure fluid producers is operated it will move said member so that both brake motors may be operated by the pressure fluid producer operated.

9. A tractor steering control comprising a brake mechanism for each of the two driving wheels of a tractor; pressure fluid actuated means for each brake mechanism; a pressure fluid producer for each brake mechanism; a valve interposed between said pressure fluid actuated means and said pressure fluid producers; a speed control device adjustable to a plurality of positions; a movable means in said valve; and 25 2,394,343

means to operably associate said speed control device with said movable means so that when said speed control device is in certain adjusted positions said movable means will be so positioned as to enable said brake mechanisms to be independently operated by the associated pressure fluid producer, said speed control device when in other positions of adjustment being dissociated from said movable means so that it may then be moved by either one of said pressure fluid producers, the-pressure producer selected then operating both brake mechanisms, and said movable means preventing transmission of pressure fluid to the inactive pressure producer.

ARTHUR N. MILSTER.

I REFERENCES CITED UNITED STATES PATENTS Number Name Date 1,987,435 Engel -'Jan. 8, 1935' 2,362,521 Acton Nov. 14, 1944 Vorech Feb. 5, 1946 

